The present invention relates generally to electro-mechanical actuators, more particularly, to an electro-mechanical actuator including a brushless DC motor for providing pinch protection.
Pinch protection is a desirable feature in a variety of electro-mechanical actuator configurations for moving a movable element between open and closed positions. In such configurations, the movable element presents a hazard associated with the possibility of compressing or pinching an obstruction between the element and a housing or frame as the element moves to a closed position. Absent pinch protection, a person may be injured, for example, if a part of his body is inadvertently xe2x80x9cpinchedxe2x80x9d between the element and a corresponding housing the element is closing against. In addition, system damage may occur to the motor or internal actuator mechanisms if the closing element is closed on some other robust obstruction.
In a specific example, it is desirable to provide pinch protection in a window lift actuator system that drives a car window between its open and closed position. When the car window is closing, a safety hazard may result if a person""s hand or finger is positioned between the window and the door frame. Some other robust obstruction may also be caught in the closing window, causing damage to the window and/or the window lift actuator system.
A pinch protection arrangement disables the actuator in the presence of an obstruction so that the system will not cause injuries or become damaged. Some pinch protection designs have simply incorporated a low force actuator that stalls under load. Importantly, however, the actuator should be capable of closing the window with sufficient force to enable closure in adverse environmental conditions and to properly seal the window.
Unfortunately, merely limiting the amount of force applied to the element by the actuator is generally not a viable solution to the safety hazard associated with closure of the element. Despite the need to provide safe conditions during closing, it is generally necessary to close the element with sufficient force against system components, e.g. seals and gaskets, that provide resistance or that need to be compressed by the actuator during some portion of the operation. Also, environmental conditions such as temperature extremes, dust, dirt and ice in the case of a window lift actuating system and other actuator systems should not cause the system to become inoperable due to the actuator not generating sufficient closure force. For these and other related reasons, it is generally not viable to provide for safe operation merely by using a low force actuator.
Accordingly, there is a need in the art for an actuator that provides efficient and reliable pinch protection for interrupting normal operation under certain conditions. There is a further need in the art for an actuator that safely and reliably closes a car window in a window lift actuator system.
An electro-mechanical actuator consistent with the invention includes: a brushless DC motor for driving an output of the actuator; and a motor controller. The controller is configured to interrupt operation of the motor in response to at least one feedback signal representative of a motor parameter that varies with variation in a load on the output. The feedback signal may be representative of motor current and/or motor speed. A feedback signal representative of motor speed may be the motor rotational position. A rotational position feedback signal may also be used for identifying zones of output movement wherein pinch protection is enabled/disabled. In one embodiment, the actuator output may be coupled to a window lift mechanism for moving a vehicle window between open and closed positions. Motor operation may be interrupted in response to a feedback signal representative of a motor parameter that varies with variation in a load on the window.
A method of providing pinch protection in vehicle window lift system for moving a vehicle window between open and closed positions consistent with the invention includes; providing a brushless DC motor for driving an output of an actuator, the output being coupled to a window lift mechanism for moving the window between the open and closed positions; sensing at least one parameter of the motor that varies with a variation in a load on the window; and disabling the motor when the parameter reaches a predetermined level. In one embodiment, the method may further include: identifying at least one zone of travel for the window wherein pinch protection is enabled; determining if the window is in the zone; and disabling the motor in the disabling step if the window is in the zone.